1. Field of the Invention
The present invention relates to the shaping of sheets of deformable material such as glass using a deformable vacuum mold of novel construction. More particularly, the present invention relates to the shaping of glass sheets to a complicated bend having opposite longitudinal sides bent to different shapes simultaneously while a sheet undergoing bending is in contact with a deformable vacuum mold. Most particularly, the present invention relates to a novel construction of means to distort a deformable vacuum mold used to shape sheets of deformable material to complicated shapes.
2. Description of Patents of Interest
U.S. Pat. No. 4,277,276; U.S. Pat. No. 4,297,118 and U.S. Pat. No. 4,349,375, all to John D. Kellar and Gordon F. Pereman, disclose the bending of glass sheets while supported in engagement against a deformable vacuum mold. In these patents, a hot, flat glass sheet is brought into engagement against a lower wall of a vacuum mold that is apertured so that air can be sucked in through the apertures of the lower wall to hold a flat glass sheet in engagement against the lower wall. Means is provided to deform the vacuum mold and shape its lower wall to a shape corresponding to that desired for a bent glass sheet. The glass sheet is softened sufficiently prior to its vacuum engagement against the lower wall of the vacuum mold so that when the mold deforms, the sheet supported thereagainst by vacuum also deforms. In the first two patents, elongated beams with curved lower edges are provided to guide the shape developed by distorting the vacuum mold. These beams require replacement to enable the apparatus to conform the deformable mold to a different production pattern. The third patent deforms the vacuum mold by a linkage arrangement that develops a series of bends of gradually increasing departure from a flat configuration toward the opposite longitudinal ends.
When continuous cams are used to engage the distorting vacuum mold, their ability to control the distortion of the deformable vacuum mold must be adjusted exactly at the beginning of a campaign for a particular pattern. It is very difficult to adjust the shape of improperly shaped cams that engage the upper wall of the vacuum mold. Since it is necessary to match the shape of the glass periphery to the outline shape of a mounting frame of a vehicle to which the bent glass sheet is bonded during fabrication of a vehicle or during replacement of a damaged window with a replacement window, the present invention has found it easier to obtain conformance of the bent glass sheet to a pattern when the shape of the deformable vacuum mold is further controlled by means other than the continuous cams of the prior art, which are not amenable to modification once their mold guiding shape is established.
U.S. Pat. Nos. 4,197,108 and 4,272,274 to Frank et al. disclose apparatus for bending glass sheets into cylindrical bends wherein glass sheets are conveyed into a shaping station on conveyor rolls and are lifted on a grooved shaping mold having a plurality of spaced elongated shaping members extending completely across a dimension of the shaping apparatus. The shaping members are separated by grooves that extend completely across the dimension of the mold, so that when the grooved shaping mold is lifted from a position beneath the conveyor rolls to a position above the conveyor rolls, the lifted glass sheet immediately above the mold sags by gravity to conform to the shape of the elongated shaping areas between the continuous elongated grooved portions. The glass is lifted into vacuum engagement against a downwardly facing wall of an upper vacuum mold having a downwardly facing wall of desired fixed configuration, the lower lifting mold is lowered to below the level of the conveyor rolls and a ring-like member is transported into the shaping station below the upper vacuum mold and above the conveyor rolls to enable the shaped glass sheet to be transferred by releasing the vacuum that supports the bent glass sheet against the lower wall of the upper vacuum mold. Preferably, the upper vacuum mold is moved vertically to a position near the conveyor rolls initially to minimize the lifting required for the lower mold, and then the vacuum mold is lifted while the lifting mold is lowered after the upper vacuum mold engages the rising glass sheet by vacuum.
In both types of apparatus described previously, the glass has been limited in its shaping to a relatively easy to accomplish shape about one axis of curvature. The need for more complicated shapes made it necessary for the glass sheet bending art to improve on the apparatus existing at the time of the present invention.